1. Field of the Invention
The present invention relates to a method and apparatus for inspecting entities comprising liquid-filled containers for one or more test parameters of the liquid, the container, or both, by rotating and axially line scanning said entities and comparing said scans electronically, after which defective entities, i.e. entities for which one or more test parameters fall outside the approved ranges are identified and separated from non-defective entities, i.e. entities for which all test parameters fall within the approved ranges.
Generally, the method and apparatus for inspecting liquid-filled containers for rejection or approval according to the present invention is useful in e.g. the quality control of cartridges or vials containing liquid pharmaceuticals or other liquids.
Particularly, a method and apparatus for reliable inspection of several test parameters simultaneously including both stationary and dynamic type parameters of the entity to be inspected, i.e. the liquid, the container, or both, is of particular value in fast control of large batches of entities particularly when a high throughput, a high probability of rejecting defective entities, and a low probability of rejecting non-defective entities is required.
In the present context the expression, "line scanning" is intended to designate the collection of information from a line of segments on the container, including information from the liquid, the container, or both, each individual segment being scanned successively using a selfscanning linear CCD array. Lines of segments may be axial or non-axial related to the axis of rotation of the entity to be inspected depending on the relationship between the rate of rotation and the scanning rate of individual segments.
Also, within the present context the expression, "test parameters" is intended to designate measured parameters which reflect the quality of each entity to be inspected in such a way that their outcome results in either rejection or approval of the inspected entity. Examples of test parameters are parameters for detection of unacceptable defects such as dirt and cracks; amount of liquid, presence of air, concentration of solutes, presence of foreign particles and bodies, and the like.
Further, within the present context the expression "stationary parameters" is intended to designate parameters that do not change during rotation, e.g. parameters that are associated with the container such as the shape of the container, the cap, the amount of liquid, etc. Inspection of these parameters is designated "container inspection". The expression "dynamic parameters" is intended to designate parameters that change during rotation, e.g. parameters that are associated with movable foreign bodies such as suspended particles and impurities in the liquid. Inspection of these parameters is designated "foreign body detection".
2. Prior Art Disclosure
Methods and apparatus for inspecting liquid-filled containers for various parameters are known. However, to the applicant's knowledge, no prior art document discloses a method or an apparatus that performs a combined inspection of parameters, stationary or dynamic, by rotating the entity to be inspected according to a predetermined rate profile and simultaneously line scanning the entity axially.
U.S. Pat. No. 3,598,907 discloses object inspection by successively televised images wherein successive images of a rotating object are compared electronically to generate an error signal whenever the difference between successive images does not fall within a predetermined range. Also, U.S. Pat. No. 3,777,169 discloses a method and means based on rotation for detecting foreign particles in liquid-filled containers by means of a video camera capable of generating several video voltage patterns or frames.
Generally, these prior art apparatus suffer from a number of disadvantages. In particular, the apparatus are based on a video or analog sensing mechanism such as a conventional television camera which usually generates a surplus of data. Also, the frame rate of a television camera is very low (20 Hz) which creates aberration of a fast rotating particle and results in low sensitivity.
U.S. Pat. No. 4,136,930 discloses a method and apparatus based on rotation for a high-speed in-line bottle inspection apparatus comprising several television cameras for detecting foreign particles in full bevarage containers moving along a conveyor. Besides foreign particle detection the apparatus may be used for detecting proper fill levels of containers, detecting the proper content of pallets or cases for warehouse control, container identification, bottle sorting and other optical comparisons of which none are disclosed. However, besides the above mentioned drawbacks of known television camera based apparatus, the accuracy of detection is reduced due to electrical differences and misalignment errors between the cameras placed at different places in space and images obtained at different times.
German Laid-Open Application No. 2820661 A1 discloses a foreign body detection apparatus based on rotation that is independent of the particle con-figuration but which does not provide for other test parameters. Further, this known apparatus uses a collimated light source and detector apparatus for projecting the particle onto the sensor. Thus, this technique is not applicable for light-scattering liquids such as suspensions or emulsions in which cases the probability of rejecting defective entities becomes unacceptable low.
Thus, besides not being able to combine reliable detection of both stationary and dynamic parameters, all the above mentioned prior art techniques fail to provide reliable foreign body detection in non-transparent liquids such as suspensions or emulsions. In these cases, the incident light may not penetrate very far into the liquid and thus detection of foreign bodies in the bulk of a suspension or an emulsion is not achieved with prior art techniques.
Further, none of the above prior art techniques of inspecting liquid-filled containers discloses a method or an apparatus suitable for inspection of one or more test parameters of the liquid, the container, or both, simultaneously at a very high throughput having a high probability of rejecting defective containers and a low probability of rejecting non-defective containers.